What Is Shear Wall?
Shear wall is a vertical element used to resist lateral forces such as wind and seismic forces act on a building structure. It works as a vertical cantilever beam supported at the ground carrying vertical load together with columns. Shear walls are mainly used in tall buildings.
In the past two decades, shear walls became an important part of high rise buildings. As a part of an earthquake building design, these walls are provided in building plans to reduce lateral displacements under earthquake loads.
Purpose Of Shear Walls:
Shear walls are mainly used
1. To resist lateral loads of earthquake and wind.
2. To resist gravity or vertical loads due to its self-weight and other living or moving loads.
3. To resist shear as well as uplift forces on building.
4. To enhance the strength and stability of a structure.
5. To provide adequate stiffness to the structure.
Location Of Shear Wall:
There are mainly two arrangements of shear walls; one is placed at the edges of the building which could be either plane or flanged shape. The other is placed inside the building in the shape of core walls or channel section.
In highrise buildings, shear walls are generally located at the center of the building normally in the form of core wall system to accommodate vertical translation systems such as lift.
Forces On Shear Wall:
Shear walls mainly resist two types of forces;
1. Shear force.
2. Uplift force.
Shear forces are produced in buildings due to ground movement and lateral forces such as wind and waves. These forces act throughout the height of the wall between the top and bottom shear wall connections.
Uplift forces are produced on shear walls due to horizontal forces act on the top of the wall. These forces try to lift up one end of the wall and push the other end down. Uplift forces create a greater effect on tall short walls and less effect on low long walls. Sometimes, shear walls require hold down devices to provide necessary uplift resistance.
Classification Of Shear Walls:
1. Simple rectangular types and flanged walls.
2. Coupled shear walls.
3. Rigid frame shear walls.
4. Framed walls with in filled frames.
5. Column supported shear walls.
6. Core type shear walls.
Types Of Shear Walls:
1. RC Shear Wall:
This is the most common type of shear wall which consists of reinforced concrete walls and RC slabs. The thickness of the walls varies from 140 mm to 150 mm. These walls are generally continuous throughout the building’s height. However, discontinuous walls might be constructed on the street from or basement level for parking space.
2. Steel Plate Shear Wall:
Generally, steel plate shear walls consist of steel plates, boundary columns, and horizontal floor beams. The steel plate wall and boundary columns act as vertical plate girder where the column act as flanges and steel plates act as its web. These types of shear walls can be used effectively in highly seismic areas. However, it may be more expensive than other types of shear wall.
3. Plywood Shear Wall:
Plywood shear walls consist of plywood, chords and base connections. Plywoods transfer shear forces, chords resist tension and compression and base connections transfer shear to the foundation.
4. RC Hollow Concrete Block Masonry Wall:
These walls are constructed by providing steel reinforcement both in the vertical and horizontal directions of masonry blocks. RHCBM walls counter lateral seismic loads and safely withstand earthquakes, This construction system is known as shear wall diaphragm concept. It gives three-dimensional stability to a building.
5. Midply Shear Wall:
It is a new concept in shear wall design. One ply of sheathing material is placed at the center of the wall between a series of pairs of studs and plates oriented in 90° rotated position relative to these in standard shear walls. To prevent brittle failure at the end stud due to high tension forces, steel rods are used at each end of the midply wall. Midply walls have superior survival characteristics under earthquake loading and have dynamic load-carrying capacity of more than three times compared to standard shear walls.
Advantages Of Shear Walls:
The various advantages of shear walls are listed below:
1. Shear walls provide more strength, stability and stiffness to a building.
2. Reduce lateral sway of a building.
3. Easy to construct and easily implemented at site.
4. Thinner walls, hence lightweight.
5. Effective in minimizing earthquake damage in structural and non-structural elements.
7. Fast construction.
8. Best performance.
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